\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{algorithmic}
\usepackage{algorithm}
\usepackage{amssymb}

\title{Algorithmicness}
\author{Yijun Hu}
\date{\today}

\begin{document}

\maketitle

\section{The Algorithm}

Here, we want to run an algorithm. Suppose we have a number $n \in \mathbb{Z}$, the algorithm will run as follows.

\begin{algorithm}
    \begin{algorithmic}
        \STATE $i = 0$
        \STATE $n$ for some $n \in \mathbb{Z}$
        \WHILE{$i \leq n$} 
            \PRINT $i$
            \STATE $i = i + 2$
        \ENDWHILE
    \end{algorithmic}
    \caption{Print all even numbers from 0 to $n$}
    \label{even0ton}
\end{algorithm}

\end{document}